Preparation of 2-cyclopentenyl ethers

ABSTRACT

Bis-(2-cyclopentenyl) ethers are prepared by contacting a 2-cyclopentenyl carboxylate or 2-cyclopentenol with an aqueous acid solution having a pH in the range of about 1.0 to about 3.0.

This is a division of Ser. No. 823,750 filed Aug. 11, 1977.

BACKGROUND OF THE INVENTION

This invention pertains to the preparation of bis-(2-cyclopentenyl)ether from 2-cyclopentenyl carboxylates and/or 2-cyclopentenol as wellas mixed ethers.

Bis-(2-cyclopentenyl) ether when epoxidized affords a commercialcycloaliphatic epoxide as described in U.S. Pat. No. 2,973,373. The useof this epoxy resin is described in U.S. Pat. No. 2,935,488.

Bis-(2-cyclopentenyl) ether was first synthesized by David et al. [Bull.Soc. Chim. France (5) 11, 5614 (1944)] employing the procedure shownbelow: ##STR1##

Several features of the above synthesis make it costly to conduct on acommercial scale. Expensive corrosion-resistant equipment is required inboth steps because the process employs hydrogen chloride as a reactantand produces sodium chloride as a by-product. Chloride ion even inneutral or basic medium, causes severe pitting of stainless steel.Secondly stoichiometric amounts of both HCl and base are consumed whichadds to the cost of the products. Thirdly malodorous by-products areformed contaminating the waste aqueous salt solution and producingunpleasant air-borne odors.

When one attempts to add a weak acid such as water or acetic acid to thedouble bond system of cyclopentadiene no formation of the desired2-cyclopentenyl compound is observed, and the eventual sole product isdicyclopentadiene. This dimerization requires no catalyst.

When a strong acid other than anhydrous HCl or HBr is used, either instoichiometric or catalytic amounts, a rapid polymerization ofcyclopentadiene occurs.

DESCRIPTION OF THE INVENTION

A method which avoid the corrosion problems inherent in the use ofhydrogen halides, does not require a stoichiometric amount of base,produces no inorganic by-products or malodorous waste streams, and canbe conducted to produce bis-(2-cyclopentenyl) ether in high chemicalefficiency has been developed which comprises contacting one part byweight of at least one 2-cyclopentenyl derivative having the formula:##STR2## wherein x is ##STR3## or H and R is H or an alkyl or cycloalkylhaving one to about eight carbons or aryl having six to ten carbons,with about 0.1 to about 10 parts by weight of an aqueous solutioncontaining about 0.01 to about 2.0 moles per liter of solution of anacid having a pKa of about 2 to about 3, at a temperature of about 0° C.to about 100° C.

The 2-cyclopentenyl derivative may be either an ester or an alcohol. Thepreparation of both of these 2-cyclopentenyl derivatives has beendescribed in the literature. Thus for example, Gilmore et al. in theJournal of the Chemical Society, 1971, 2355-7, describes the preparationof 2-cyclopentenyl acetate in 70 percent yield by the interaction ofcyclopentene with acetic acid using stoichiometric amounts of manganicacetate or potassium permanganate. Shono et al. [Tetrahedron Letters,59, 6207-8 (1968)] describes the anodic oxidation of cyclopentene inacetic acid in a 41% yield. Dane et al. [Ann. 532, 28-39 (1937)]prepared 2-cyclopentenyl acetate from cyclopentene, selenium dioxide andacetic anhydride. Dane et al. [Ann. 539, 207-12 (1939)] obtained2-cyclopenentyl acetate from cyclopentene, lead tetraacetate and aceticacid. U.S. Pat. No. 3,632,633 issued to Louvar discloses the preparationof 2-cyclopentenyl acetate from cyclopentene and acetic acid over azeolite catalyst.

Baltz et al. [East German 81650] obtained 2-cyclopentenol fromcyclopentene and tertiary-butyl hydroperoxide in the presence of arhodium catalyst. Criegee et al. [Ber. 721, 1799 (1939)] oxidizedcyclopentene with oxygen and ultraviolet light to the correspondinghydroperoxide which was then reduced with sodium sulfite to thecorresponding 2-cyclopentenol.

Where a cyclopentenyl ester is used as the starting material, it ispreferred that R be methyl, that is, the product derived fromcyclopentene and acetic acid. However other acids may also be used suchas formic, propionic, butyric, valeric, hexanoic, heptanoic, octanoic,isobutyric, benzoic, cyclohexanecarboxylic acids and the like.

As a variation of this reaction mixed 2-cyclopentenyl ethers may beobtained by adding an equivalent amount of a primary or secondaryalcohol as part of the charge. Primary aliphatic alcohols having about 1to 4 carbon atoms are preferred. These are exemplified by allyl alcohol,methallyl alcohol, ethyl alcohol, n-propyl alcohol, n-butyl alcohol andthe like. Secondary alcohols afford lower yields than primary alcoholsbut can be used. The secondary alcohols can be aliphatic orcycloaliphatic, as for example, isopropyl alcohol, 2-butanol,cyclohexenyl alcohol, and the like. Tertiary alcohols, however, do notserve as suitable substrates in this reaction.

It was surprising to observe that the mixed 2-cyclopentenyl ethers canbe prepared with a high degree of specificity because for some reason,not understood, the addition of the primary or secondary alcohol to thereaction mixture inhibits the formation of bis-(2-cyclopentenyl) ether,allowing a higher yield of a single product ether.

Although a ratio of about 0.1 to about 10 parts by weight of the aqueousacid solution can be used per part of the 2-cyclopentenyl derivative, itis preferred to use a range of about 0.2 to about 3 parts by weight ofaqueous solution.

Although the concentration of acid can range from about 0.01 to about2.0 moles per liter of solution, it is preferred to use a range of about0.05 to about 0.5 moles of acid per liter of solution.

Aqueous solutions are derigueur since it was unexpectedly found that inthe absence of water little or no ether is formed.

Although the reaction can be run at a temperature of about 0° C. toabout 100° C., the preferred range is about 10° to about 50° C.

Pressure is not narrowly critical and so while it is preferred to carryout the claimed method at atmospheric pressures for economic reasons, itcan also be run at superatmospheric or subatmospheric pressures ifdesired.

Time is not narrowly critical but for commercial applications reactiontimes of about 1 to 3 hours are found to be convenient affordingsatisfactory yields of bis-(2-cyclopentenyl) ether or mixed ethers. Thetime required depends on the temperature and the particular catalystsolution used.

The acid concentrations used in the claimed method afford aqueoussolutions with a pH in a range of about 1 to about 3. This is a criticalfactor required to prevent the formation of cyclopentadiene polymers asan undesirable side reaction, which is favored by strong acids. Theacidic compounds used to afford this range of pH cover a wide spectrumof materials. Thus, for example, one can use alkali metal bisulfates andother bisulfates, oxalic acid, maleic acid, fumaric acid, sulfamic acid,trichloroacetic acid, picric acid, Lewis acids such as boron trifluorideand the like which are hydrolytically stable, and acid salts of primary,secondary or tertiary amines and quarternary ammonium hydroxides withdi- or polybasic acids. Illustrative acid salts are: pyridiniumbisulfate, triamylammonium bisulfate, benzyltrimethylammonium bisulfate,tetrabutylammonium bisulfate, tetrabutylammonium hydrogenm-benzenedisulfonate, tetrabutylammonium pyrophosphate, partialtrioctylammonium salts of polyphosphoric acid, and the like. Otheracidic compounds having ionization constants in the range of about1×10⁻² to about 1×10⁻³ i.e., a pKa of about 2 to about 3, will bereadily apparent to those skilled in the art can also be used.

As a variation of this method one can go through a hydrolysis oralcoholysis step converting 2-cyclopentenyl ester to 2-cyclopentenolbefore conversion to the desired product, bis-(2-cyclopentenyl) ether.

The invention is further described in the examples which follow. Allparts and percentages are by weight unless otherwise specified.

The terms "conversion", "yield" and "chemical efficiency" are usedherein according to the following definitions: ##EQU1## S_(f) =Mols ofstarting material fed to the reactor. S_(r) =Mols of starting materialremaining at the end of the reaction.

P=mols of product formed.

I_(r) =Mols of any intermediates remaining at the end of the reaction.

EXAMPLE 1 2-Cyclopentenyl acetate by oxidation of cyclopentene witht-butyl hydroperoxide in acetic acid

To a 500 ml heavy glass bottle containing a magnetic stirring bar wasadded 1.0 g (0.005 mol) of cuprous acetate and 60.0 g (1.0 mol) ofacetic acid. The mixture was stirred to dissolve the salt. Then 68.0 g.(1.0 mol) of cyclopentene, 31.9 g (0.33 mol) of 93.8 percent t-butylhydroperoxide, and an accurately weighed amount of chlorobenzene as aninternal standard were added. The bottle was capped, and the reactionmixture was stirred at 70° C. for 20 hours and the contents thenanalyzed by gas chromatography using an OV-17 column [50%phenylmethylsilicone on an inert support] temperature programmed for80°-220° C. at 8° per minute. Quantification of results was accomplishedby relating the chromatographic peaks to that of the chlorobenzene andtaking into consideration the response factors previously determinedwith authentic samples of the individual components of the reactionmixture. The analysis showed a 65% yield of 2-cyclopentenyl acetate anda 4.3% yield of 2-cyclopentenol. Only small amounts of 3 unknowncompounds were present. In order to determine if any resinous orhigh-boiling by-products not detectable by gas chromatography hadformed, the crude reaction product mixture was flash distilled in arotary evaporator at a flask temperature of 140° C. and a final pressureof 10 torr. The weight of the residue was approximately equal to theweight of cuprous acetate catalyst that had been used in the reaction.This demonstrated that only a very small amount of organic residue hadbeen formed.

EXAMPLE 2 Isolation of 2-cyclopentenyl acetate

Nine preparations of 2-cyclopentenyl acetate were conducted using theamounts of starting materials and the conditions described in Example 1with the omission of the chlorobenzene internal standard. The crudeproducts were combined and stripped of unreacted cyclopentene bydistillation in a rotary evaporator. The remaining material was flashdistilled rapidly under reduced pressure to eliminate the coppercatalyst and any high-boiling residues and was then fractionallydistilled through a spinning band column. Cyclopentenyl acetate,assaying 97.8% purity by gas chromatography, was isolated as a fractionboiling at 40° C. at 8 torr and having a refractive index (n_(D) ²⁵) of1.4455. The total yield of 2-cyclopentenyl acetate in the distillationfractions was 65% of the theoretical.

EXAMPLE 3 2-Cyclopentenol by methanolysis of 2-cyclopentenyl acetateusing sodium methylate catalyst

To a test tube containing a mini magnetic stirring bar was added 500 mg(3.9 millimoles) of 2-cyclopentenyl acetate and a sodium methylatesolution prepared by dissolving 9.2 mg (0.4 millimoles) of sodium metalin 800 mg (25 millimoles) of methanol. The tube was stoppered and thesolution stirred at 40° C. for 2 hours. To the solution was then added aweighed amount of 1,4-dioxane to serve as a chromatographic standard,and the mixture was then analyzed by gas chromatography using an"Apiezon" column, temperature programmed from 80° to 220° C. at 8° perminute. The analytical results, corrected for response factors of thecomponents, showed that 2-cyclopentenol had been formed in a yield of99%. Methyl acetate was formed as the co-product. The data of thisExample are recorded in Table 1 below.

EXAMPLES 4-8

The procedure in Example 3 was repeated using the following methanolysiscatalysts: magnesium methylate, sodium hydroxide, calcium oxide, andDowex 1-X4 in the methoxide form. Dowex 1-X4 is an anion exchange resinsold in the chloride form. To convert it into the methoxide form it wasplaced in a burette and subjected to a continuous flow of sodiummethylate solution until the effluent gave a negative test for chlorideion. Dry methanol was then passed through the bed to eliminate residualsodium methylate. The resin was stored with methanol. In Example 8 Dowex1-X4 was used in the hydroxide form. This was prepared by treating thechloride form with an aqueous solution of sodium hydroxide and thenpassing dry methanol through the resin solumn to eliminate sodiumhydroxide and water. The data of Examples 4-8 are recorded in Table 1below.

                                      TABLE I                                     __________________________________________________________________________    2-Cyclopentenol by Methanolysis of 2-Cyclopentenyl Acetate                    Example                                                                            Catalyst        Methanol                                                                           CPOAc                                                                              Time                                                                             Temp.                                                                            CPOH Yield                               Number                                                                             Type     mM    mM   mM   (hrs)                                                                            °C.                                                                        mM %                                     __________________________________________________________________________    3    NaOCH.sub.3                                                                            0.4   25   3.94 2  40°                                                                        3.91                                                                             99                                    4    Mg(OCH.sub.3).sub.2                                                                    0.3   15   3.90 18 40°                                                                        2.85                                                                             73                                    5    NaOH     0.4   16   4.03 1  40°                                                                        3.66                                                                             91                                    6    CaO      0.2   43   3.84 2  40°                                                                        3.65                                                                             97                                    7    Dowex.sup.+ OCH.sub.3.sup.-                                                            0.2g(dry)*                                                                          44   3.99 2  40°                                                                        3.68                                                                             94                                    8    Dowex.sup.+ OH.sup.-                                                                   0.05g(dry)*                                                                         10   3.98 2  40°                                                                        3.82                                                                             96                                    __________________________________________________________________________     CPOAc = 2-Cyclopentenyl acetate                                               CPOH = 2-Cyclopentenol                                                        *Dowex catalyst was added to reaction mixture wet. The dry weight was         determined by filtering off the catalyst at the end of the run and drying     and weighing it.                                                         

EXAMPLE 9 Etherification of 2-cyclopentenol using aqueoustetrabutylammonium bisulfate catalysts

To a test tube with a mini magnetic bar was added 0.02 g (0.06millimoles) of tetrabutylammonium bisulfate and 0.25 g (14 millimoles)of water. The bisulfate was first dissolved in the water, and then 0.336g (4.00 millimoles) of 2-cyclopentenol was added. The test tube wasstoppered and the mixture was stirred at 40° C. for 3 hours.

For quantitative analysis of the products, a weighed amount of dioxane(internal standard) was added along with sufficient acetone tosolubilize the mixture. Analysis of the products was carried out by gaschromatography using an "Apiezon" column at 80°-220° C., temperatureprogrammed at 8° per minute. Bis-(2-cyclopentenyl) ether was obtained ina yield of 88 percent and an efficiency of 99 percent. Pertinent dataare recorded in Table II.

EXAMPLE 10 Etherification of 2-cyclopentenol using aqueous sodiumbisulfate catalyst

Example 9 was repeated with the exception that sodium bisulfate was usedas the catalyst in place of tetrabutylammonium bisulfate. Pertinent dataare recorded in Table II.

CONTROL A Etherification of 2-cyclopentenol using dry tetrabutylammoniumbisulfate catalyst

Example 9 was repeated with the exception that dry tetrabutylammoniumbisulfate was used as the catalyst. No reaction occurred. It is thusevident that water is necessary for the reaction even when the startingmaterial is a 2-cyclopentenol rather than a 2-cyclopentenyl ester.Pertinent data are recorded in Table II.

                                      TABLE II                                    __________________________________________________________________________    Etherification of 2-Cyclopentenol                                             (All reactions conducted at 40° C. for 3 hrs.)                         Starting Materials                 Product                                    Example                                                                             Catalyst     H.sub.2 O                                                                            2-Cyclopentenol                                                                       Bis-(2-cyclopentenyl) ether                 Number                                                                              Type  g  mM.sup.(1)                                                                        g  mM.sup.(1)                                                                        g   mM.sup.(1)                                                                        Yield %                                                                            Efficiency %                           __________________________________________________________________________    9     Bu.sub.4 NHSO.sub.4                                                                 0.02                                                                             0.06                                                                              0.25                                                                             14  0.3362                                                                            4.0 87.8 99.1                                   10    NaHSO.sub.4                                                                         0.007                                                                            0.06                                                                              0.30                                                                             17  0.2776                                                                            2.7 32.6 41.2                                   Control A                                                                           Bu.sub.4 NHSO.sub.4                                                                 0.02                                                                             0.06                                                                              none   0.2304                                                                            2.7 no reaction                                 __________________________________________________________________________     .sup.(1) Millimoles.                                                     

EXAMPLES 11-13 Bis-(2-cyclopentenyl) ether from 2-cyclopentenyl acetate(one-step)

In a series of small-scale experiments, 0.5 gram samples of2-cyclopentenyl acetate were stirred with aqueous solutions oftetrabutylammonium bisulfate. At the end of the reaction period, dioxane(internal standard) was added in weighed amounts. Acetone was added toconvert the two layers of the reaction mixture into a single phase. Theresulting solution was analyzed by gas chromatography. The results aregiven in Table III.

EXAMPLE 14 Bis-(2-cyclopentenyl ether) from 2-cyclopentenyl acetate(one-step)

2-Cyclopentenyl acetate (9.9 grams, 79 millimoles) was added to asolution of tetrabutylammonium hydrogen sulfate (0.40 grams, 1.23millimoles) in 10 grams of water. The mixture was stirred at 40° C. for6 hours, and the two layers were then separated and analyzed using thepreviously described technique of empolying 1,4-dioxane as an internalstandard. Sulfur analysis to determine distribution oftetrabutylammonium hydrogen sulfate between the two layers was conductedby x-ray fluorescence. The analytical results are summarized below. (Thefollowing conventions are used: mM=millimoles; CPOH=2-cyclopentenol;CPE=bis-(2-cyclopentenyl) ether; and CPOAc=2-cyclopentenyl acetate).

                                      TABLE III                                   __________________________________________________________________________    Bis-(2-Cyclopentenyl) Ether from 2-Cyclopentenyl Acetate Using Bu.sub.4       NHSO.sub.4 Catalyst                                                                Charge         Conditions                                                                            Yield                                                                                      Efficiency*                          Example                     Bis-(2-cyclo-                                                                         2-cyclo-                                                                           to bis-(2-cyclo-                     No.  CPOAc                                                                              H.sub.2 O                                                                         Bu.sub.4 NHSO.sub.4                                                                 Temp                                                                              Time                                                                              pentenyl) ether                                                                       pentenol                                                                           pentenyl) ether                      __________________________________________________________________________    11   0.5g 1.0g                                                                              0.02g 40°                                                                         3 hrs.                                                                           41.6%   35.0%                                                                              96.0%                                12   0.5g 0.25g                                                                             0.02g 24°                                                                        20 hrs.                                                                           40.4%   31.6%                                                                              89.7%                                13   0.5g 0.25g                                                                             0.02g 40°                                                                         4 hrs.                                                                           33.7%   24.4%                                                                              82.5%                                __________________________________________________________________________     *Efficiency calculations take credit for 2-cyclopentenol as an                intermediate since it can be recycled for production of additional ether.

                           Tetra-                                                                        butyl-                                                                        ammonium                                                                            Acetic                                                                  hydrogen                                                                            Acid CPOH CPE  CPOAc                             __________________________________________________________________________                           sulfate                                                                Oil Layer                                                                            0.02 mM                                                                             15.0 mM                                                                            10.4 mM                                                                            29.8 mM                                                                            16.1 mM                                           Water Layer                                                                          1.28 mM                                                                             44.6 mM                                                                             6.2 mM                                                                             0.6 mM                                                                             1.4 mM                                           Total  1.30 mM                                                                             59.6 mM                                                                            16.6 mM                                                                            30.4 mM                                                                            17.5 mM                           __________________________________________________________________________

These data demonstrate that essentially all of the tetrabutylammoniumhydrogen sulfate catalyst remained in the aqueous layer. Thus, theaqueous layer could be recycled after removal of at least part of theacetic acid (by extraction or other suitable means). The extract canthen be combined with the oil layer for isolation of the cyclopentenylether by distillation. Fractions containing 2-cyclopentenol and/or2-cyclopentenyl acetate can be recycled to the etherification reaction.

EXAMPLES 15-23 Bis-(2-cyclopentenyl ether) from 2-cyclopentenyl acetate

The procedure described for Examples 11-13 was employed for evaluationof various catalysts for the one-step conversion of 2-cyclopentenylacetate to bis-(2-cyclopentenyl) ether. The results are presented inTable IV.

                                      TABLE IV                                    __________________________________________________________________________    Bis-(2-cyclopentenyl) ether from 2-cyclopentenyl acetate                       Example                                                                            ##STR4##                                                                              H.sub.2 O                                                                        Catalyst  Time    Conv                                                                              Yield                                                                             Eff                                No.  (g)     (g)                                                                              (g)    pH (hrs)                                                                             Temp                                                                              (%) (%) (%)*                                __________________________________________________________________________    15   0.5     0.25                                                                             oxalic acid                                                                          1.3                                                                              3.0 40°                                                                        63  29  71                                                  0.006                                                         16   0.5     0.25                                                                             Picric acid                                                                          1.6                                                                              3.0 40°                                                                        71  21  47                                                  0.014                                                         17   0.5     0.25                                                                             Maleic acid                                                                          1.9                                                                              3.0 40°                                                                        61  21  49                                                  0.08                                                          18   0.5     0.25                                                                             BF.sub.3.Et.sub.2 O                                                                  1.9                                                                              5.0 24°                                                                        86  16  34                                                  0.01                                                          19   0.5     0.25                                                                             H.sub.3 PO.sub.4                                                                     1.9                                                                              4.0 40°                                                                        73  16  26                                                  0.0033                                                        20   0.5     0.25                                                                             HCl    1.3                                                                              2.0 40°                                                                        70  30  63                                                  0.0035                                                        21   0.5     0.25                                                                             Bu.sub.4 NHSO.sub.4                                                                  1.6                                                                              5.0 24°                                                                        30  7   99                                                  0.020                                                         22   0.5     0.25                                                                             Bu.sub.4 NHSO.sub.4                                                                  1.6                                                                              18.0                                                                              24°                                                                        60  37  98                                                  0.020                                                         23   0.5     0.25                                                                             Cl.sub.3 CCOOH                                                                       1.2                                                                              3   40°                                                                        66  17  51                                                  0.01                                                          __________________________________________________________________________     *Efficiencies are calculated on basis of taking credit for co-produced        2-cyclopentenol as a starting material.                                  

EXAMPLE 24 Alcoholysis of 2-cyclopentenyl acetate and etherification of2-cyclopentenol to bis-(2-cyclopentenyl) ether

This reaction was carried out in two steps but without the internemdiateisolation of 2-cyclopentenol. In the first step, 2-cyclopentenyl acetatewas converted to 2-cyclopentenol using a basic catalyst as described inExample 8. In the second step the 2-cyclopentenol was converted tobis-(2-cyclopentenyl) ether using an acidic catalyst.

Step 1: To a 50 ml. round-bottom flask with a magnetic stirring bar wasadded 9.92 grams (78.7 mols) of 2-cyclopentenyl acetate, 29 grams ofmethanol and 0.75 grams of Dowex 1-X4 resin in the methoxide form. Theflask was stoppered and the contents stirred at 40° C. for 2.5 hours.Gas chromatographic analysis showed that 2-cyclopentenol was formed ingreater than 95 percent yield. The resin catalyst was removed byfiltration, and the product solution was stripped at 60° C. under vacuumto remove the unreacted methanol and the methyl acetate formed. Gaschromatographic analysis showed that approximately 10 percent of themethanol was still present in the residue.

Step 2: To the 50 ml round-bottom flask containing the residue (6.8grams) from the distillation in step 1 was added 5 grams of water and0.5 grams of tetrabutyl ammonium hydrogen sulfate. The flask wasstoppered and the contents stirred at 40° C. for 3 hours. To the flaskwas then added chlorobenzene as an internal standard and acetone tosolubilize the mixture. Gas chromatographic analysis was carried outthrough an OV-17 column, at 80°-220° C., temperature programmed at 8°per minute. The results showed a 61.1 percent yield ofbis-(2-cyclopentyl) ether, a 12.2 percent yield of 2-cyclopentenol, 2.5percent of unreacted 2-cyclopentenyl acetate, and the remaining 24percent as 2-cyclopentenyl methyl ether that was formed by the reactionof methanol (present in the residue from distillation) with2-cyclopentenol.

2-Cyclopentenol reacts with methanol in the presence of an acidiccatalyst forming 2-cyclopentenyl methyl ether. By eliminating themethanol completely in the stripping operation at the end of Step 1, ahigher yield of bis-(2-cyclopentenyl) ether can be produced.

CONTROL B Attempted etherification of allyl alcohol using aqueoustetrabutylammonium bisulfate catalyst

To 5.0 g of allyl alcohol was added a solution of 0.20 g oftetrabutylammonium bisulfate in 6.0 g of water. The clear solution washeated under reflux (90° C.) for 16 hours. The mixture was then cooledand analyzed by gas chromatography using an Apiezon column programmedfrom 80° to 220° C. The only peak exhibited was that for allyl alcohol.No diallyl ether had been formed.

EXAMPLE 25 Allyl 2-cyclopentenyl ether from allyl alcohol and2-cyclopentenyl acetate using aqueous tetrabutylammonium bisulfatecatalyst

To a mixture of 2-cyclopentenyl acetate (0.3 g, 2.4 millimoles) andallyl alcohol (0.5 g, 8.6 millimols) was added a solution of 0.02 g oftetrabutylammonium bisulfate in 0.3 g of water. The mixture, in astoppered test tube, was stirred magnetically while being heated at 40°C. for 3 hours. At the end of this reaction period, acetone was added toproduce a homogeneous solution for analytical purposes, and a sample wasexamined by gas chromatography using a "Carbowax-20M" column programmedfrom 80° to 220° C. The following peaks were observed:

    ______________________________________                                                         RETENTION                                                    COMPOUND         TIME          AREA %                                         ______________________________________                                        Acetone           62 seconds   54.5                                           Allyl alcohol    204 seconds   15.3                                           Allyl 2-cyclo-                                                                pentenyl ether   302 seconds   5.2                                            2-Cyclopentenyl acetate                                                                        390 seconds   19.3                                           2-Cyclopentenol  422 seconds   3.6                                            Acetic acid      500 seconds   0.8                                            2-Cyclopentenyl ether                                                                          590 seconds   0.4                                            ______________________________________                                    

The mass spectrum of the material having a retention time of 302 secondswas in full agreement with the mixed ether structure assigned to it. Nodiallyl ether was obtained in this experiment, and it is also noteworthythat very little bis-(2-cyclopentenyl) ether was formed.

EXAMPLE 26 Catalytic alcoholysis of 2-cyclopentyl acetate by passagethrough a bed of ion exchange resin

A solution of 1.80 g (0.014 mol) of 2-cyclopentenyl acetate in 3.80 g(0.12 mol) of methanol and 0.700 g of chlorobenzene (the internalstandard for chromatographic analysis) was slowly passed through ajacketed column containing 20 ml of Dowex 1-X4 (an anion exchange resinof the quaternary ammonium type) in the hydroxide form in methanol. Thecolumn was maintained at 56° C. by refluxing acetone in the jacket. Theresin was then rinsed with methanol, and the combined effluent andrinsings were analyzed by gas chromatography using a 6-ft. OV-17 columnprogrammed from 80° to 220° C. The analysis showed that 2-cyclopentenolhad been formed in 96% yield and essentially 100% efficiency. Noby-products were observed.

The total residence time of the reaction mixture in the ion exchangeresin bed was less than 5 minutes.

EXAMPLE 27 2-Cyclohexenyl 2-cyclopentenyl ether

A two-phase reaction mixture containing 2-cyclopentenyl acetate (0.30 g,2.4 millimols), 2-cyclohexenol (0.50 g, 5.1 millimols),tetrabutylammonium hydrogen sulfate (0.020 g, 0.06 millimols), and water(0.25 g, 13.9 millimols) was heated at 40° C. with vigorous stirring forfour hours. Acetone was then added to give a one-phase system foranalytical purposes, and the solution was analyzed by gas chromatographyusing an Apiezon column programmed from 60° to 220° C. The followingrelative peak areas were observed for the cyclic components:

    ______________________________________                                        2-Cyclopentenol          5.9                                                  2-Cyclohexenol           70.2                                                 2-Cyclopentenyl acetate  20.8                                                 Bis-(2-Cyclopentenyl) ether                                                                            0.3                                                  2-Cyclohexenyl 2-cyclo-                                                       pentenyl ether           2.8                                                                           100.0                                                ______________________________________                                    

No bis-(2-cyclohexenyl) ether and only a small amount ofbis-(2-cyclopentenyl) ether were formed. Although the yield of mixedether was low (approximately 7% of the theoretical), the chemicalefficiency for a process based on this procedure is high since thecyclopentenol, cyclohexanol, cyclopentenyl acetate, andbis-cyclopentenyl ether can all be recycled to increase the yield ofmixed ether.

EXAMPLE 28 2-Cyclopentenyl 2-methylallyl ether

A mixture of 2-cyclopentenyl acetate (0.30 g) and 2-methylallyl alcohol(0.40 g) was stirred vigorously at 40° C. for 4.5 hours with a solutionof 0.020 g of tetrabutylammonium bisulfate in 0.25 g of water. Acetonewas added at the end of the reaction period, and the solution wasanalyzed by gas chromatography using an Apiezon column programmed at60°-220° C. The yield of 2-cyclopentenyl 2-methylallyl ether, estimatedfrom peak areas, was 40%. No peaks corresponding to bis-(2-methylallyl)ether to bis-(2-cyclopentenyl) ether were observed.

EXAMPLE 29 n-Butyl 2-cyclopentenyl ether

2-Cyclopentenyl acetate (0.30 g) and n-butanol (0.40 g) were mixed andstirred vigorously at 40° C. for 4 hours with a solution of 0.020 g oftetrabutylammonium hydrogen sulfate in 0.25 g of water. At the end ofthe reaction period acetone was added to give a single phase, and thesolution was analyzed by gas chromatography using an Apiezon columnprogrammed at 60°-220° C. Peaks for the cyclic compounds had thefollowing relative areas.

2-Cyclopentenol: 15

2-Cyclopentenyl acetate: 65

Butyl 2-Cyclopentenyl ether: 20

From this it was estimated that the mixed ether had been formed in 17%yield.

EXAMPLE 30 2-Cyclopentenyl isopropyl ether

1-Cyclopentenol (0.30 g), isopropanol (0.40 g), and an aqueous solutionof 0.020 g of tetrabutylammonium hydrogen sulfate in 0.25 g of waterwere mixed, and the two-phase system was stirred vigorously at 40° C.for 4 hours. Acetone was then added to homogenize the mixture, and itwas analyzed by gas chromatography. Peaks corresponding to about a 6%yield of 2-cyclopentenyl isopropyl ether and about a 12% yield of2-cyclopentenol were observed along with a concomitant peak for theco-product acetic acid. No bis-(2-cyclopentenyl) ether was formed.

CONTROL C Attempted preparation of t-butyl 2-cyclopentenyl ether

A mixture of 2-cyclopentenyl acetate (0.3 g) and t-butanol (0.4 g) wasstirred vigorously for 5 hours at 40° C. with a solution of 0.02 g oftetrabutylammonium bisulfate in 0.025 g of water. At the end of thereaction period, acetone was added to homogenize the mixture foranalysis by gas chromatography. The only peaks corresponding to cycliccompounds were those corresponding to 2-cyclopentenol (about 20% yield),unreacted 2-cyclopentenyl acetate, and a trace of bis-(2-cyclopentenyl)ether. Separate gas chromatographic analyses were conducted usingApiezon (60°-220° C.) and Carbowax-20M (60°-220° C.) columns with athermal conductivity detector and using Carbowax and OV-1 columns inseries (60°+4°/minute) with a flame ionization detector to eliminateinterference by the peak for water. In none of these analyses was anypeak for t-butyl 2-cyclopentenyl ether observed.

The experiment was repeated using 0.01 g of sodium bisulfate as thecatalyst in place of the quaternary ammonium salt. As before, no peakcorresponding to t-butyl 2-cyclopentenyl ether was observed in the gaschromatographic analysis.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure has been made only by way of example and that numerouschanges can be made without departing from the spirit and scope of theinvention.

What is claimed is:
 1. Method of preparing mixed 2-cyclopentenyl etherswhich comprises contacting one part by weight of at least one2-cyclopentenyl derivative having the formula: ##STR5## wherein X is##STR6## or H and R is H or an alkyl or cycloalkyl having 1 to about 8carbons or aryl having 6 to 10 carbons and an equivalent amount of aprimary or secondary alcohol having 1 to about 6 carbons with about 0.1to about 10 parts by weight of an aqueous solution containing about 0.01to about 2.0 moles per liter of solution of an acid having a pK_(a) ofabout 2 to about 3, at a temperature of about 0° C. to about 100° C. 2.Method claimed in claim 1 wherein the primary alcohol is allyl alcohol.3. Method claimed in claim 1 wherein the primary alcohol is2-methylallyl alcohol.
 4. Method claimed in claim 1 wherein the primaryalcohol is n-butyl alcohol.
 5. Method claimed in claim 1 wherein thesecondary alcohol is 2-cyclohexenol.
 6. Method claimed in claim 1wherein the secondary alcohol is isopropyl alcohol.